Children with autism and autism spectrum disorder (ASD) suffer from defects in socialization, verbal and nonverbal communication, and response to sensory stimuli. While the cause of autism is unknown, children with autism and ASD have been noted in several studies to have a high prevalence of macrocephaly, appear to be taller on average than the general population, and may have gastrointestinal co-morbidities for which gluten- and/or casein-free diets are prescribed. Growth patterns and markers of maturation in autistic children have not been studied in detail, and other methods of assessing maturation in autistic children, such as hormone analyses and bone age, have not been explored. Cross-sectional data are being used to assess growth and maturation of children with autism/ASD in three ways: 1) the height, weight, body mass index (BMI) and head circumference of 81 children (75 boys) with autism/ASD between 4 and 8 years of age in comparison with developmentally normal age-, gender-, and race-matched controls, 2) DHEA-S levels and other significant growth hormones (IGF-1, IGF-2, IGFBP3) in children with autism/ASD in comparison with the same developmentally normal controls, and 3) bone age and second metacarpal morphometry in children with autism/ASD in comparison with reference populations. Preliminary analyses have indicated several significant clinical findings. First, the autism/ASD cases had significantly greater head circumference, weight, and body mass index than controls, although height did not differ significantly between groups. The case groups mean levels of IGF-1, IGF-2, IGFBP3 and GHBP were all significantly higher, and significantly more of the cases had DHEA-S levels in the detectable range. Future studies should examine the potential role of growth-related hormones in the pathophysiology of autism and childhood development of children with autism/ASD. Second, boys with autism or ASD also showed a progressive fall-off or slowing of appositional bone growth between 4 and 8 years, with the discrepancy being significant by age 6 years. The effect was strongest for children on casein-free diets. The bone development of children with autism/ASD at these ages should be monitored carefully as part of routine care, especially if they are on casein-free diets.